(1) Field of the Invention
The present invention relates to an inking device for a printing machine, which has both a follow-up mechanism of a nip pressure to the shift of a plate cylinder and a nip pressure adjusting mechanism operable from the outside while the machine operates.
(2) Description of the Related Art
Heretofore, an inking device mounted on a printing machine, such as a rotary printing machine, is provided with an ink fountain and a number of rollers. The ink reserved in the ink fountain, is taken up by rotating the roller to adhere the ink to the surface of the roller in the state of an ink film. Subsequently, this ink film is uniformed and kneaded in various directions while transferred among a number of rollers, and then it is supplied to a plate surface on a plate cylinder by a form roller.
In such an inking device, there is a fear that a contact pressure between the form roller and the print surface, viz. a nip pressure is varied owing to the change in the diameter of the form roller by the thermal expansion and abrasion thereof, the finish state of the plate cylinder, and the like. Since the nip pressure largely influences the quality of prints, the nip pressure is adjusted in a printing preparation step or at the time of printing by providing the inking device with a nip pressure adjusting device.
An example of such a nip pressure adjusting device is disclosed in Japanese Utility Model Publication No. 34670/1995 suggested by the applicant of the present invention. In this device, as shown in FIG. 6, when a drive piece 100 is rotated, for example, clockwise from the outside while the machine is running, a drive rod 103 rotates clockwise via a control rod 101 and a universal joint 102. At this time, a pull rod 105 is pulled into a nut 104 at the right end of the drive rod 103 by its screw action, and a lever 106 rotates counterclockwise to thus reduce the nip pressure (a contact pressure between a form roller 107 and a plate cylinder 108). On the contrary, when the drive piece 100 is rotated counterclockwise, the pull rod 105 is delivered from the nut 104 and hence the lever 106 rotates clockwise to increase the nip pressure.
On the other hand, at the time of roller-lifting (which separates the form roller 107 from the plate cylinder 108 temporarily), the lever 106 rotates counterclockwise. In this case, there is, deformed under compression, a compression coil spring 109 which is wound around the pull rod 105 to push the form roller 107 against the plate cylinder 108 through the lever 106, and the drive rod 103 slides into the universal joint 102 to allow the lever 106 to rotate. The above description is made with regard to the lever 106 on the upper and this side in the figure. Now, referring to a lever 106 on the lower and this side (this is similar to the lever 106 on the upper and far side), obviously it is slightly different from the above lever 106 in that the pull rod 105 is replaced by a push rod 110 as a constitution of the lever angle changing means and the position of the compression coil spring 109 is altered to thereby become changed in the direction of action, because the rotational direction of the lever for increasing/decreasing a nip pressure is opposite to that of the above case. The numerals 111 and 112 in FIG. 6 denote an aggregation rubber barrel and ink rollers, respectively.
In the printing machine, when the print surface is mounted on the plate cylinder, it likely occurs that the print surface gets slightly twisted in relation to the plate cylinder and both the right and left ends of the print surface are twisted in the opposite circumferential directions of the plate cylinder, thereby making the right-and-left register inconsistent. To cope with this, a so-called twist adjustment is conducted in such a way that the inconsistent register is changed proper by shifting an eccentric bearing which rotatably supports the rotational shaft of the plate cylinder on the frame of the printing machine.
However, in a conventional nip pressure adjusting device, since the twist adjustment of the plate cylinder changes the nip pressure already adjusted, it requires to readjust the nip pressure. Accordingly, the applicant of the present invention has before presented the inking device in Japanese Laid-Open Patent Publication No. HEI 3-207653 wherein a nip pressure remains unchanged even after a twist adjustment of a plate cylinder to dispense with a readjustment of a nip pressure.
In this inking device, as shown in FIG. 7, in which a cam driving means is not shown, when not in printing operation, shifts a cam 123 in relation to a plate cylinder 122 in such a way that the driving means pushes a cam-follower 121 upwardly and away from the plate cylinder 122 while resisting a biasing force caused by a compression coil spring 120. Hence, a form roller 124 is parted from the plate cylinder 122 to become non-contact. In printing operation, the cam driving means shifts the cam 123 in relation to the plate cylinder 122 so that the form roller 124 may be pushed against the plate cylinder 122 to become firmly in contact therewith by a biasing force of the compression coil spring 120.
At the time of printing, when a rotary lever 125 is moved by an adjusting screw 126, the position of the cam follower 121 is changed in relation to a roller arm 127 because the cam follower 121 is eccentrically supported on the supporting axis of the rotary lever 125. Accordingly, the relative rotational position of the cam follower 121 to the form roller 124 supported by the roller arm 127 is changed. Hence, the form roller 124 is moved in the radial direction of the plate cylinder 122 and consequently a pressure of the form roller 124, applied to the print surface (a nip pressure), is changed.
When a twist adjustment is conducted, since the cam 123 mounted on the plate cylinder 122 is moved together with the cam 122, the cam follower 121 pushed against the cam 123 is also moved simultaneously. Accordingly, before and after the twist adjustment, the relative positional relation between the form roller 124 and the plate cylinder 122 is not altered, and then the biasing pressure, viz. the nip pressure therebetween remains unchanged.
However, in the nip pressure adjusting device, as described above in FIG. 6, it is provided with the nip pressure adjusting mechanism that can be controlled from the outside when the machine is in running, but it is not provided with any follow-up mechanism for a nip pressure capable of coping with a movement of the plate cylinder. Hence there is a problem that a nip pressure is changed when the plate cylinder is moved. In the inking device in FIG. 7, on the contrary, it bears the follow-up mechanism for a nip pressure for coping with a movement of the plate cylinder, but dose not bear any nip pressure adjusting mechanism that can be controlled from the outside when the machine is in running and accordingly this causes such a problem that quality of print is not improved sufficiently.
Accordingly, it is strongly required to develop an inking device which has both a nip pressure adjusting mechanism that can be controlled from the outside during the running of the machine and a follow-up mechanism of a nip pressure capable of coping with a movement of a plate cylinder, however, it has not been realized from such a reason that any form roller is positioned within an arrangement of rollers and hence an adjusting direction of a nip pressure adjusting mechanism is restricted, and the like. Taking the inking device in FIG. 7 as an example, when it is intended to dispose the knob of an adjusting screw 126 to shift the eccentric rotary lever 125 in the outside, a supporting point and an adjusting direction of the eccentric lever is restricted so that handling of each member becomes very difficult.
An object of the present invention is to provide an inking device for a printing machine, which has both a nip pressure adjusting mechanism that can be controlled from the outside during the running of the machine and a follow-up mechanism of a nip pressure capable of coping with a movement of a plate cylinder, and wherein there is a degree of freedom in handling each member for the inking device and the inking device is easily set.